Micro-indentation of metallic photonic crystals: experimental and numerical investigations

Photonic crystals (PCs) are synthetic materials that are used to control light propagation. PCs have a frequency bandgap where light is forbidden to propagate. This bandgap is strongly tied to the microstructure of the photonic crystal. Three-dimensional tungsten photonic crystal in a Lincoln-log microstructure has been suggested as a strong alternative filter in photovoltaic cells with significantly high power efficiency. PCs have also been suggested as sensors for submicron damage. Therefore, mechanical characterization of three-dimensional photonic crystals becomes of interest. Here we report on mechanical characterization of tungsten PC using means of micro-indentation. We also present a three-dimensional finite element simulation of the structural response of a Tungsten photonic crystal under micro-indentation load. Stresses developed in the PC can be used to quantify the level of damage in the crystal. We compare our simulation results with the experimental observations of a Vickers and Knoop micro-indentation experiments of tungsten PC. The FE models were proven able to simulate the mechanical response of the PC with a good accuracy. The calibrated FE models can be further used to realize the mechanical behavior of PC under different thermal and mechanical stresses when used as filters in photovoltaic cells or to simulate the effect of damage in PC sensors.     

Damage Pattern Recognition for Structural Health Monitoring Using Fuzzy Similarity Prescription

Abstract:   Structural health monitoring (SHM) is a systematic method for non-destructive evaluation of a structure's performance by sensing, extracting, patterning, and recognizing features of the structural response. Most SHM approaches focus on statistical analysis for damage identification considering only random uncertainties. This article introduces a method that allows accommodating other types of uncertainties due to ambiguity, vagueness, and fuzziness which are statistically non-describable. The proposed method deals primarily with epistemic uncertainty. The method improves damage identification by performing damage pattern recognition using fuzzy sets. In this approach, healthy observations are used to construct a fuzzy set representing healthy performance characteristics. Additionally, the bounds on the similarities among the structural damage states are prescribed. Thus, an optimal group of fuzzy sets representing damage states such as little, moderate, and severe damage can be inferred as an inverse problem from healthy observations only. Piecewise linear functions are used as fuzzy membership functions representing the states of healthy and damaged. The optimal group of damage fuzzy sets is used to classify a set of observations at any unknown state of damage using the principles of fuzzy pattern recognition based on maximum approaching degree. A case study for damage pattern recognition of a model steel bridge is presented and discussed. The approach is capable of identifying damage patterns accurately.     

Seismic response control of asymmetric buildings using tuned mass dampers

The aim of the present study is to investigate the efficiency of the torsional tuned mass dampers (T‐TMDs) in response control of asymmetric buildings under bidirectional earthquake ground excitations. The efficiency of the T‐TMDs is compared with bidirectional tuned mass dampers (BTMDs). The T‐TMDs are oriented to the rotation of the structures about vertical axis with a single torsional mass attached to spring–dashpot elements, whereas the BTMD connects a single mass to two orthogonal sets of spring–dashpot elements oriented to principal axes of the building. The buildings are idealized three‐dimensional models with two translational and one torsional degrees of freedom for each floor. Three different configurations (cruciform‐shaped, L‐shaped, and T‐shaped) of multistory buildings are considered. The 5‐, 15‐, and 20‐story buildings with and without the tuned mass damper schemes are subjected to bidirectional earthquake ground excitation. In order to evaluate the effectiveness of the T‐TMDs and BTMD, the rotation, displacement, acceleration, and base shear force responses are computed. Parametric studies are conducted for all the configurations installed with the T‐TMDs and BTMD by varying their mass ratio, damping ratio, and ground motions. It is concluded that the T‐TMDs are more effective in mitigating the torsional response of asymmetric buildings as compared with the BTMD.     

Reduction of IgE Immunoreactivity of Whole Peanut (Arachis hypogaea L.) After Pulsed Light Illumination

Pulsed light (PL), a novel food processing and preservation technology, has been shown in literature to reduce allergen levels on peanut, soybean, almond and shrimp protein extracts. This study investigated how PL affected the immunoreactivity of whole peanut kernels at two sample-to-lamp distances (7 and 10 cm) and a PL frequency of 3 pulses/s. A combination of different illumination durations and distances were tested to explore the effective conditions for PL roasting of whole peanuts. After the PL treatments, crude protein of the whole peanuts was extracted and compared to that of the raw peanuts (control) in vitro for allergen reactivity using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot, dot blot, and enzyme-linked immunosorbent assay (ELISA) with pooled plasma of allergenic patients. The SDS-PAGE, Western blot, dot blot results all showed that PL was capable of mitigating all major allergens of whole peanut kernels to an undetectable level. Indirect ELISA results showed 80 % signal reduction for the PL-treated peanut as compared to raw peanut. A closer distance (7 cm) between the PL lamp and the sample resulted in stronger reduction of IgE immunoreactivity than 10 cm.     

Protein co-precipitates: A review of their preparation and functional properties

Advances in protein co-precipitation technology over the past two decades have made it possible to commercially produce different types of proteins from mixtures of raw materials. Incorporation of protein co-precipitates improves the functional (e.g. appearance, texture, and stability) and nutritional characteristics of many food products. Increasing world population, increasing demand for and cost of protein-rich foods, and the continuing need to improve the nutritional and functional properties of protein ingredients have contributed to greater research into blends or composites as food ingredients. Protein co-precipitates have a range of biological, physical, chemical, functional, sensory and nutritional properties giving the potential application as ingredients in the food industry, though relatively little published information is available on this subject. There is limited information about the use of protein co-precipitates by the food industry when developing products for different groups of potential consumers. The aim of this review is to evaluate the current status of protein co-precipitate research as a potential way of improving utilization of protein rich raw materials (e.g. dairy protein), oil seed meals (e.g. sesame, soybean, flaxseed and canola) and by-products (e.g. brewing yeast). By blending proteins from different sources, protein co-precipitates are a way of overcoming deficiencies in essential amino acid contents found in proteins from a single source, which giving ingredients with good functional properties and desirable sensory characteristics.     

WCDMA uplink capacity of high-altitude platforms (HAPs) macrocells with incorporated HSUPA service

The multiservice (voice, data, and high-speed uplink packet access (HSUPA)) uplink capacity and the interference statistics of high-altitude platforms wideband code-division multiple access macrocell are studied. The free-space propagation loss model with a log-normal shadowing is used in the analysis. It is concluded that the voice and data service are significantly affected by HSUPA users and that the macrocell capacity decreases dramatically when one of these users gets connected to it in the case that they share the same frequency band. Also, it is concluded that the capacity decrement is highly sensitive to the location of the HSUPA users. When the HSUPA users did not share the same frequency band with the voice and traditional data users, macrocell capacity will be 3 HSUPA users with a processing gain of 8 or 5.3 HSUPA users with a processing gain of 16.     

Enhanced removal of Methylene Blue by electrocoagulation using iron electrodes

The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. The study deals with the enhancement of removal of Methylene Blue dye by using an electromagnetic field during the electrocoagulation process. Effects of electrolyte concentration, dye concentration, intensity and the direction of the electromagnet on the decolorization efficiency have been investigated. The formed ferric hydroxide flocs trap colloidal particles and make solid–liquid separation easier during the next stage. The electrocoagulation stages must be optimized in order to design an economically feasible process. The results showed that the optimum electrolysis was 10–20 min at a current density of 8 mA/cm², while the optimum concentration of the electrolyte (NaOH) was found to be 2 wt.% when the dye concentration was 50 mg/L. The utilization of an electromagnetic field enhanced the dye removal due to the induced motion of paramagnetic ions inside the solution. The power consumption required to remove the dye was reduced by 45% in the case of applying an electromagnetic field.     

Electrophilic iododestannylation of <Emphasis Type="Italic">N</Emphasis>-(4-(2-azanorborn-2-yl)butyl)-4-trimethylstannylbenzamide as a route to a novel radioiodinated compound for malignant melanoma

N-(4-(2-Azanorborn-2-yl)butyl)-4-[¹²⁵I]iodobenzamide was prepared by the reaction of its trimethylstannyl precursor with Na¹²⁵I in the presence of various oxidizing agents such as lactoperoxidase, Chloramine T, and Iodogen. The effect of reaction parameters such as temperature, reaction time, oxidizing agent concentration, pH, and substrate concentration was examined. The stability of the labeled product was evaluated. Chromatographic analysis of the reaction mixture by TLC using ethanol: ethyl acetate (1: 1) and by HPLC using methanol: water (55: 45) as eluent showed that the optimum radiochemical yield of the final product is 94% and the radiochemical purity is 99%. Also HPLC chromatographic analysis showed that the content of undesired by-products, especially of chlorinated products, in case of Chloramine T was higher than that in case of other oxidizing agents. With the lactoperoxidase method, the amount of undesired by-products was minimal and, therefore, the radiochemical purity was high.     

Investigation of flax fibre reinforced epoxy friction composites

The use of eco‐materials on the basis of natural fibre reinforced polymer composites has found its way to many applications. In the automobile sector, the use of such composites has long been established for applications in the car interior. The use of natural fibre reinforced composites for braking applications has however not been confirmed yet. In this study the use of flax fibres as a candidate reinforcement substitution for glass or even the carcinogenic asbestos fibres has been investigated. Typical frictional materials such as alumina, iron and brass particulates have been used together with graphite as a lubricant. Epoxy resin was used as the binding matrix. Results show frictional behaviours comparable with commercially available brake linings at acceptable wear rates.